Most of my trotting is done on the Trent which being very wide is mostly silvery, so , my first choice is usually black as I can see it yards n yards downstream. On occasions however a particularly high floodbank or tree makes black impossible for a short while until the float clears the shaded portion of river-- a small circle of white paint below the black makes little differance so at times I find myself counting the time it takes for the float to clear and if it is "late" in appearing I strike which gives up the occasional fish or two.
If the swim is a long one and its dark and light water intermittantly I will opt for orange as I find this is see-able in both sets of circumstances, not as easy as black but not bad all the same, Red is not bad but its a second choice for me if i can avoid it.
Lately I have been using white on the river if the water is a dull shade but once the sun gets on it particularly when its sinking into the west it simply dissapears. A hot lemony green is also good, I have found a little hobby shop in Sheffield that does the very small tins similar to Humbrol that was around but is now hard to find (have they stopped making it ?)I go along with the temporary painting of floats but does anyone remember the little soft plastic tips of differant colours that were simply pushed onto a float tip that were around back in the sixties/seventies -- really really useful bit of kit-- I would love a couple of sets to go in my float box but I dont think they are made anymore, a real shame.